Can we go back in the time using spacetime machine?

Can we go back in the time using spacetime machine

One of the most intriguing questions we've all wondered about when we were kids is whether we can travel into the future or go back in time using some sort of time machine

Still Remains intriguing Even in our adult lives and fortunately for US science has advanced to the point where we can answer this Age old question we can easily travel forward in time and we've known how to do that since 1905. Einstein's special theory of relativity lays out the whole recipe of how you can move into the future and all you have to do is go into sort of a lower gravity field relative to other people or just travel very fast and your clock will tick slower than that of everybody else that you've left behind then when you return you'll be younger than your twin for example if you had left your twin back on Earth so in that sense you are travelling into the future that's easy to do and we've known how to do that travelling backwards that's the problem we think we can do that I have some colleagues who've made some calculations that assert that depending on a trajectory you take around a black hole you can come out and end up in the past of when you started but that takes extraordinary setup to make happen but right now no problem travelling into the future we've known the answer that it is absolutely possible to travel forwards in time.

Infact we have irrefutable evidence to show that so before we dwell into the intricacies of going back in time first let's see why scientists are so confident we can travel into the future the faster you move the slower time ticks for you as others view it relative to the Observer you don't know anything's happening your clock still ticks as far you've still got your your heart beat.

All of this, so this is not a physiological thing it is an actual property of the fabric of space and time under those conditions so I watch you fly by and the faster you go the slower time ticks for you so not only does speed do this, also the strength of a gravitational field will have the same effect on you.

Initially when formulated you're thinking, it's just because you're moving it's actually way deeper than that. The GPS satellites orbit higher than our space station the geosynchronous satellites are like middle orbit that is far enough away from Earth's source of gravity for them to have a difference a measurably different space-time condition so that their clocks tick faster than our clocks on Earth surface because they're farther away.

Their time takes faster relative to us but we get precise timings from geosynchronous satellites.

How does this work? We pre-correct the time signal from the GPS satellites to compensate for Einstein's general theory of relativity, so that by the time the time reaches us it's been properly corrected and it matters to us and our space-time Continuum not the one that's in Middle Earth orbit what once you calculate that then you do and you say, oh my gosh! the formula Works! Einstein was right.

It is true [Music] in physics and relativity time dilation is the difference in the elapsed time as measured by two clocks is either due to a relative velocity between them or to a difference in gravitational potential between their locations.

For example near the vicinity of a black hole to a distant Observer, clocks near a black hole would appear to tick more slowly than those farther away from the black hole due to this effect known as gravitational time dilation.

An object falling into a black hole appears to slow as it approaches The Event Horizon taking an infinite amount of time to reach it as we said.

Besides the difference in gravitational potential, there is another way to travel into the future and that is going through space in relativistic velocities as you approach the speed of light, something really strange starts to happen let's keep going faster and faster ninety percent the speed of light 99 the speed of light time is ticking slower and slower and slower for you you will watch the whole future history of the universe unfold in front of your eyes, as fractions of a second go by, for you as you go 99 99.9 99.99 the speed of light, there's a formula for this of course special and general relativity suggests that suitable geometries with space-time or specific types of motion in space might allow time travel.

Not only into the future but also into the past however time travelled into the past is theoretically possible in certain general relativity space-time geometries only when travelling faster than the speed of light is permitted and the problem with going back in time is forgetting about the other side of the coin of the space-time Continuum which is space it's not good enough just to travel back in time you need something to propel you in space as well so it's a space time a space-time machine not just a time machine because Earth is a moving Target.

I just want to make that clear and by the way just to go back in time you could still land on Earth but how was Earth rotated you can end up in Siberia in the middle of the ocean probably because most of Earth's longitude is spanned by ocean.

So it's truth in time travel with regard to these space-time coordinates now we call these your coordinate in space and your coordinate of time we call that your world line another problem with going back in time using a time machine or a space-time machine is the so-called grandfather Paradox but what is it exactly you cannot go back in time and prevent your parents from meeting each other because then you would have never been born to have gone back in time to have prevented your parents from meeting each other.

This is the fundamental Paradox of time travel and so if there were a rule book that'd be number one rule perhaps the best way to go back in time is to make use of wormholes the theory of general relativity does suggest a scientific basis for the possibility of backward time travel in certain unusual scenarios so going through a traversable wormhole could in theory allow you to go back in time.

So we have the sort of the fabric of the space-time Continuum it's not just that space is out there, space is intricately configured with time and how do you know this space time are forever conjoined? This fabric can be distorted in such a way that you can change the distance the space-time distance between two locations and one way to imagine that is imagine all of our universe is just on a flat sheet of paper.

You're on one edge of the paper and I want to get to the other Edge and I'll take out light years of time whatever, however long that takes it's light years distance. So, I take many years travelling at the speed of light but if I take the space and warp it curve it back

on itself now your location is very close to me if I could somehow punch through the fabric of space and time, and reach your location something that would otherwise be longer a shorter distance and thereby transcending the speed of light.

To do so you're no longer limited by the speed of light the diameter of our galaxy is a hundred thousand light years you can't travel across it unless you figure out a way to warp space and time so in that warp in principle on paper you can have a hole that you pass through and just come out the other side and you're in another place, and if you did it right you can show up at another time and that's the most classical invocation of a wormhole.

Another approach for backwards time travel involves a dense spinning cylinder usually referred to as, a Tipler cylinder discovered as a solution in general relativity this hypothetical cylinder is infinitely long and Spins fast enough about its long axis and a spaceship flowing around, the cylinder or a spiral path could travel back in time or forward depending on the direction of the Spiral however, the density and speed required is so great the ordinary matter is not strong enough to construct it.

By the way if you manage to travel someplace faster than light you have the capacity to move backwards in time we've got that one established as well, we just don't have any easy way to travel faster than light but one way that's been celebrated in science fiction, and you can write it out on paper legitimately is a wormhole.

A wormhole I'm over here and I want to get over there and I want to get there quickly you can travel through a wormhole that

changes the effective distance between where you are and where you're going and then you sort of look around when you get there and you find, oh my gosh? I've travelled a hundred thousand light years in a matter of a moment when you do that you have the capacity to move backwards in time relative to when you left now you don't get to visit yourself you're in a sort of a different space-time trajectory so you can't shake hands with yourself before you left.

And by the way there's a huge Paradox that people worry about and many people including Stephen Hawking, the late Stephen Hawking worried whether this Paradox would prevent backwards time travel completely because, if you go back in time and prevent your parents from meeting one another then they wouldn't have ever given birth to you to go back in time to prevent them from meeting one another.

Thanks for reading.

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